ANS Flashcards
Parasympathetic Pre-Ganglionic neurons leave the CNS via:
- Cranial Nerves
- Sacral Nerves
Location of Parasympathetic Ganglion:
Located at/near the target organ (contains ell bodies of post-ganglionic neurons)
Sympathetic Pre-Ganglionic neurons leave the CNS via the:
- Thoracic Level
- Lumbar Level
Location of Sympathetic Ganglion:
Located in sympathetic chain ganglion (paravertebral columns)
Sympathetic Chain
Collection of ganglia next to the vertebral column
Pathway of Sympathetic Fibers
Sympathetic pre-ganglionic fibers leave spinal cord –> synapse on dendrites/cell bodies of post-ganglionic neurons –> axons of post-ganglionic neurons go to their target organ and synapse there
What NT is released from both Parasympathetic and Sympathetic Pre-Ganglionic Neurons?
Acetylcholine (ACh)
Receptor on both Parasympathetic and Sympathetic Post-Ganglionic Neuron:
Nicotinic Receptor
The ____ has the specific connections to control the ANS and many __-___ cell bodies are located there.
- Hypothalamus
- Pre-Ganglionic
Location of Nicotinic Cholinergic Channels
Dendrites of the post-ganglionic neurons (in whatever ganglia) used by the system
Effect of Nicotinic Cholinergic Channels
- Binding of ACh opens the channel on post-ganglionic neuron
- Na+ enters the cell
- Typical EPSP
- Generation of APs on post-ganglionic neuron
The En-Passant Synapse
- Found at the synapse between post-ganglionic axons in the ANS and the target organ
- Contains swellings on post-ganglionic neuron; same machinery found in pre-synaptic terminal (ex. mitochondria, vesicles with NTs)
Parasympathetic Post-Ganglionic Axon Synapse on Target Tissue:
- NT: ACh
- Receptor on Target Tissue: Muscarinic
Muscarinic Cholinergic Receptors
- Increase IP3/DAG –> increase intracellular Ca2+ via Gq/11 activation
- 3 types found in the CNS: M1R, M3R, M5R
Muscarinic Cholinergic Receptor: M1R
- Found in CNS
- When activated in salivary glands, increase secretion
- When activated in stomach, increase acid secretion
Muscarinic Cholinergic Receptor: M3R
- When activated on smooth muscle, contractions
- When activated on exocrine glands (including sweat glands), increase secretion
Muscarinic Cholinergic Receptor: M5R
Found in CNS, not ANS
Muscarinic Receptors
- Inhibit adenylyl cyclase –> decreases cAMP
- Two types: M2R, M4R
Muscarinic Receptors: M2R
Found in cardiac conduction system: allows K+ efflux and slows conduction
Alpha 1 Adrenergic Receptors
- Gq/11 coupled
- Lead to increased Ca2+ intracellularly
Location of Alpha 1 Adrenergic Receptors
- Smooth muscle of blood vessels (contraction)
- Smooth muscle of urinary and reproductive tracts
- Liver (glycogenolysis; gluconeogenesis)
- Adipose tissue (lipolysis)
- Lacrimal glands (reduced watery secretion)
- Radial muscle of iris (contraction of muscle leads to dilation of pupil)
Alpha 2 Adrenergic Receptors
- Gi/o couple
- Lead to decreased adenylate cyclase/cAMP
Location of Alpha 2 Adrenergic Receptors
- Majority are pre-synaptic and reduce NE release
- GI sphincters (relaxation)
- Pancrease (increased glucagon, decreased insulin)
- Smooth muscle of blood vessels (dilation)
- Platelets (increased clotting)
Beta 1 Adrenergic Receptors
- Gs coupled
- Lead to increased adenylate cyclase activity and cAMP production
Location of Beta 1 Adrenergic Receptors
- Cardiac Tissue: SA Node = increased heart rate, Ventricular muscle = increased strength of contraction
- Salivary glands (increased viscous secretion)
- Adipose Tissue (increased lipolysis)
Beta 2 Adrenergic Receptors
- Gs coupled
- Lead to increased adenylate cyclase activity and cAMP production
Location of Beta 2 Adrenergic Receptors
- Bronchiole smooth muscle (relaxation)
- GI smooth muscle (relaxation)
- Urinary/reproductive smooth muscle (relaxation)
- Vascular smooth muscle (relaxation)
- Liver (glycogenolysis)
- Eye (relaxation of ciliary muscles which flattens lens and increases ability to see far away)
Beta 3 Adrenergic Receptors
- Gs coupled
- Lead to increased adenylate cyclase activity and cAMP production
Location of Beta 3 Receptors
- White adipose tissue (lipolysis)
- Brown adipose tissue (heat production)
Some sympathetic preganglionic axons pass through the sympathetic chain without synapsing on post-ganglionic neurons and instead travel to the:
Adrenal Medulla
Chromaffin Cells
- Located in adrenal medulla; preganglionic neurons synapse on these cells
- Make and release Epi as part of the sympathetic response
What NT is released from the Adrenal Gland?
Epinephrine
What receptors does Epinephrine from the Adrenal Gland bind to?
Adrenergic receptors on target cells
HEART - Sympathetic Receptors
(1) SA Node/Heart Rate
(2) AV Node Conduction
(3) Strength of Contraction
(1) Beta 1 Receptors
(2) Beta 1 Receptors
(3) Beta 1 Receptors
SA Node/Heart Rate: Function of Beta1 Receptor
Increased HR